Method and apparatus for scalable signal processing

ABSTRACT

The invention relates to content signal processing and in particular to processing of a video content signal. An apparatus ( 100 ) for content signal processing comprises a scalable encoder ( 101 ) for encoding a content signal to generate scalable encoded data comprising data associated with a plurality of compression rates. A compression processor ( 105 ) determines compression factor indicators indicating data associated with the plurality of compression rates. Thus, the compression factor indicators indicate which data of the scalable encoded data corresponds to the different compression rates. Combined data comprising the scalable encoded data and the compression factor indicators are stored in a frame memory ( 105 ). An application having a given compression factor requirement may use the compression factor indicators to access the scalable encoded data of the frame memory ( 105 ) which is required for processing. A plurality of applications may access the same frame memory ( 105 ) thereby allowing for scalable encoded data which can be used with a plurality of applications having different compression factor requirements.

FIELD OF THE INVENTION

The invention relates to a method and apparatus for content signalprocessing and in particular for processing a scalable encoded signal.

BACKGROUND OF THE INVENTION

In recent years, the use of digital storage and distribution of contentsignals such as video signals have become increasingly prevalent.Accordingly, a large number of different encoding techniques fordifferent content signals have been developed. For example, a number ofvideo encoding standards have been designed to facilitate the adoptionof digital video in many professional- and consumer applications and toensure compatibility of equipment from different manufacturers.

Most influential standards are traditionally developed by either theInternational Telecommunications Union (ITU-T) or the MPEG (MotionPictures Experts Group) committee of the ISO/IEC (the InternationalOrganization for Standardization/the International ElectrotechnicalCommittee).The ITU-T standards, known as recommendations, are typicallyaimed at real-time communications (e.g. videoconferencing), while mostMPEG standards are optimized for storage (e.g. for Digital VersatileDisc (DVD)) and broadcast (e.g. for Digital Video Broadcast (DVB)standard). Currently, one of the most widely used video compressiontechniques is known as the MPEG-2 (Motion Picture Expert Group)standard. MPEG-2 is a block based compression scheme wherein a frame isdivided into a plurality of blocks each comprising eight vertical andeight horizontal pixels. For compression of luminance data, each blockis individually compressed using a Discrete Cosine Transform (DCT)followed by quantization which reduces a significant number of thetransformed data values to zero. For compression of chrominance data,the amount of chrominance data is usually first reduced bydown-sampling, such that for each four luminance blocks, two chrominanceblocks are obtained (4:2:0 format), that are similarly compressed usingthe DCT and quantization. Frames based only on intra-frame compressionare known as Intra Frames (I-Frames).

It is desirable to reduce the resulting encoding rate as much aspossible in order to reduce the bandwidth required to transmit videosignals as well as the memory required for storage of video signals.

In recent years a large number of different video applications andprocesses have been developed which are aimed at processing of digitalvideo. These applications include for example algorithms for videoencoding and compression in accordance with the developed videostandards but also extend to a number of algorithms for processing ofvideo signals in order to derive additional information or provideadditional effects. For example, applications for content analysis orthree-dimensional information extraction have been developed.

In order to efficiently implement these algorithms and applications,many dedicated or semi-dedicated integrated circuits are beingdeveloped. As many of the developed algorithms are based on one or moreframes of the video signals, the video processing circuitry compriseframe memory which holds the data of one or more frames. Preferably, theframe memory is embedded on the same chip as the processingfunctionality as this allows for faster data transfers, increasedbandwidth and reduced power consumption.

However, as the chip size of an integrated circuit is limited, the framememory embedded is typically limited and may further vary betweendifferent integrated circuits. Additionally, in some applications, theframe memory may be external which allows it to be significantly largerthan for embedded frame memory.

Accordingly, scalable embedded compression techniques have beendeveloped which allows for a frame of a video signal to be encoded in aformat where it can be scaled to suit a given frame memory. Thus, anon-compressed frame may for example comprise 10 Mbits. If the framememory is only 2 Mbits, a scalable compression algorithm allows for the10 Mbit of data to be compressed to 2 Mbits. However, if the framememory allows only 1 Mbit of data, the algorithm may compress the frameto 1 Mbit. Thus the frame may be encoded into frame memory such that itfits the available memory capacity.

One such encoding algorithm is described in “DCT-domain embedded memorycompression for hybrid video coders” by R. P. Kleihorst and R. J. vander Vleuten, Journal of VLSI Signal Processing Systems, vol. 24, pp1523-1543, 2000, Institute of Electrical and Electronic Engineers. Thisallows for an efficient storage of frame data of a video signal.

The technique described by Kleihorst et al. provides for an efficientscalable embedded encoding which is suited for a given application.Thus, one or more frames may be encoded and stored in frame memory. Theframes may then be provided to the application and processed by this.However, currently many video signal processing techniques are known andmay be applied to video signals. Accordingly, a video signal may be usedfor several different processes and applications. For example, anencoded signal may be processed to generate three dimensionalinformation from two-dimensional pictures; to be compressed to a lowerdata rate or may be processed to derive content information. However,many of these applications or processes have different characteristicsand require different parameters of the input video signal. For example,segmentation processes may be based on frame signals which arecompressed by up to a factor of eight whereas a compression algorithmmay require that the input video signal is compressed by a factor offour or less. Thus, as different applications have differentrequirements, the technique described by Kleihorst et al. is notdirectly applicable and requires that frame data is converted into aformat suitable for the different applications having differentrequirements.

Hence, an improved method and apparatus for content signal processingwould be advantageous and in particular a system facilitating the use ofscalable embedded encoded signals with different applications orprocesses would be advantageous.

SUMMARY OF THE INVENTION

Accordingly, the Invention preferably seeks to mitigate, alleviate oreliminate one or more of the above mentioned disadvantages singly or inany combination.

According to a first aspect of the invention, there is provided anapparatus for content signal processing comprising: encoding means forencoding a content signal to generate scalable encoded data comprisingdata associated with a plurality of compression rates; means fordetermining compression factor indicators indicating data associatedwith the plurality of compression rates; and means for generatingcombined data comprising the scalable encoded data and the compressionfactor indicators. The content signal may be a video signal.

The invention allows for scalable encoded data to be generated which maybe used with a number of different applications having differentrequirements. In particular, scalable encoded data may be generated fromwhich data corresponding. to a desired or required compression factormay be extracted. The compression factor indicators indicate dataassociated with different compression rates. The invention allows fordata corresponding to a given compression factor to be extracteddirectly by use of the compression factor indicators.

The compression factor indicators may preferably include a multiplicityof indicators indicating the data corresponding to a given compressionfactor in a multiplicity of blocks. For example, the scalable encodingmay be based on grouping content data into groups of content data andencoding each group individually. Preferably, a set of compressionfactor indicators is generated for each group. For a video contentsignal, each group of data may for example correspond to a DiscreteCosine Transform (DCT) block. The compression factor indicators maydiffer between blocks as may the criteria used for determining thecompression factor indicators. For example, the algorithm fordetermining the compression factor indicators may depend oncharacteristics of the individual groups or blocks of data.

The combined data may for example be stored in a suitable data store ormay be communicated to an internal or external application. Preferably,the data associated with a plurality of compression rates comprisesoverlapping sets of data. Hence, a data section which corresponds to agiven compression factor is preferably a subset of a data sectioncorresponding to a lower compression factor. For example, if theencoding uses a DCT each compression factor may correspond to a giventruncation of the generated spatial frequency coefficients withincreasing compression factors corresponding to increasing truncations.

Hence, the invention may allow for combined data to be generated whichfacilitates use of scalable encoded data to be used for differentapplications having different compression factors.

The term compression factor may include indirect references tocompression factors such as a resulting data rate, frame memory size,compression rate or similar.

According to a feature of the invention, the apparatus further comprisesfirst processing means for processing a first application, the firstprocessing means comprising: means for determining at least a firstcompression factor associated with the first application; firstextraction means for extracting a first data set associated with thefirst compression factor of the scalable encoded data in response to thecompression factor indicators; means for processing the scalable encodeddata in accordance with the first application.

The invention thus allows for a given application to extract therequired or desired data from a scalable encoded signal. Hence, theinvention allows for a low complexity and/or flexible way ofdistributing data which may be customised by the individual applicationto suit the requirements of this application. This furthermore allowsfor a high degree of flexibility in the design and updating ofapplications since processes or algorithms utilising differentcompression factors can be introduced without requiring any changes tothe encoding of the content signal.

The determination of the at least first compression factor may be anactive determination in response to an evaluation of one or more varyingcharacteristics of e.g. the content signal, the scalable encoded data orthe application. Alternatively or additionally it may be a passivedetermination such as simply using a predetermined value for the firstapplication. Preferably a plurality of compression factors is determinedand data is extracted in response to these compression factors. Forexample, a different compression factor may be generated for differentsections or data groups of the scalable encoded data or of theunderlying content signal.

According to a different feature of the invention, the first applicationis a segmentation application. This allows for an efficient and flexibleway of performing a segmentation operation on an encoded content signal.

According to a different feature of the invention, the first extractionmeans is operable to extract the first data set in response to asegmentation determined by the first application. This allows for datato be extracted which specifically suit the characteristics of differentsegments determined by the segmentation application. Thus the processmay advantageously include a feedback loop wherein the segmentation isbased on the extraction of data and the extraction of data being refinedin view of the segmentation. For example, increased compression factorsmay be used within homogenous segments and lower compression factors maybe used between segments or within non-homogeneous sectors. Thus, thecompression factors and data to process may be optimised or improved forthe characteristics of the scalable encoded data or content signal thusallowing for a more efficient processing with reduced resourcerequirements. This is particularly advantageous for a time consistentsegmentation wherein segmentation information of previous data appliesto the current data For example, segmentation of a previous video framemay be used for extraction of a first data set of a subsequent videoframe.

According to a different feature of the invention, the apparatus furthercomprises second processing means for processing a second application,the second processing means comprising: means for determining a secondcompression factor associated with the second application; the secondcompression factor being different than the first compression factor;

second extraction means for extracting a second data set associated withthe second compression factor of the scalable encoded data in responseto the compression factor indicators; and means for processing thescalable encoded data in accordance with the second application.

Thus the invention allows for a single scalable encoded data signal tobe used for a plurality of applications having different requirementsand specifically having different associated compression factors. Theassociated compression factors may vary for different sections or groupsof the scalable encoded data or the underlying content signal. Thecompression factors may be identical in some sections while differing inother sectors. For example, the ranges of the different compressionfactors may be different for the first and second application. Hence,the invention allows for a very flexible scalable encoded data and for aflexible and efficient encoding and processing system for contentsignals.

The means for extracting data may be different means or may be the samemeans extracting data in response to the compression factors of thefirst or the second application.

According to a different feature of the invention, the first extractionmeans is operable to send data of the first data set associated with thesecond compression factor to the second processing means; and the secondextraction means is operable to extract additional data associated withthe second compression factor.

This provides for an efficient and easy to implement means of extractingdata for a plurality of applications. Specifically, this may provide fora fast and low complexity way of extracting data for two applicationswhere one set of data is a subset of the other. For example, if thesecond application requires data according to a lower compression factorthan the first application, this may require that the second applicationis supplied with the data provided to the first application plus furtherdata associated with the lower compression factor. In this approach,only one extraction operation is required for each data element even ifneeded by both applications.

According to a different feature of the invention, the secondapplication is a compression application. This allows for an efficientand flexible way of performing a compression operation on an encodedcontent signal.

According to a different feature of the invention, the second processingmeans comprises a data storage for storing the second data set andwherein the second application is operable to store compressed data inthe data storage and comprises a compression algorithm operable toperform compression in response to the stored compressed data.

This allows for an efficient compression of a content signal wherein thecompression may be based on past compressed data. For example, for avideo content signal, compression of a given frame may be in response toother compressed frames.

According to a different feature of the invention, the first applicationis a segmentation application and the first processing means is operableto provide segmentation data of the segmentation application to thesecond processing means and the compression application is operable toperform compression in response to the segmentation data. This allowsfor the compression to be in response to a segmentation thereby allowingfor an efficient compression with improved quality and/or compressionrates. For example, segments comprising homogenous data may becompressed with higher compression factors than segment transitions orsegments comprising non-homogenous data. Hence the invention allows fora flexible, efficient and/or high performance way of combining asegmentation algorithm and a compression algorithm.

According to a different feature of the invention, the first data setcorresponds to a frame of the scalable encoded data and the firstextraction means (201) is operable to extract the first data set inresponse to a segmentation of the frame. For example, an externalsegmentation process may provide segmentation information that can beused for optimising the extraction of data This allows for improved dataextraction based on only on spatial information and analysis and notrequiring temporal information.

According to a different feature of the invention, the encoding meanscomprise a single pass scalable encoder. The invention allows for asingle pass encoder to generate scalable encoded data which can be useddirectly by a plurality of applications having different compressionfactor requirements. Thus, the requirement for multiple pass encodingmay be obviated or mitigated by the invention. Hence, the complexity,computational resource, cost and/or speed of encoding may besignificantly reduced.

According to a different feature of the invention, the compressionfactor indicators comprise at least one pointer indicating a terminationpoint and/or a starting point for data associated with a givencompression factor. This provides for a particularly advantageous way ofindicating data associated with the given compression factor. It allowsfor simple implementation and simple extraction of data.

According to a different feature of the invention, the content signal isa video signal. The invention allows for an advantageous way ofgenerating scalable encoded data for a video signal which may bedirectly used by a plurality of video processing applications havingdifferent requirements of the scalable encoded data.

According to a second aspect of the invention, there is provided anapparatus for content signal processing comprising: receiving means forreceiving combined content signal data comprising scalable encoded datacomprising data associated with a plurality of compression rates andcompression factor indicators indicating data associated with theplurality of compression rates; means for determining at least a firstcompression factor associated with a first application; extraction meansfor extracting a first data set associated with the first compressionfactor of the scalable encoded data in response to the compressionfactor indicators; and means for processing the first data set inaccordance with the first application.

According to a third aspect of the invention, there is provided a methodof content signal processing comprising the steps of: encoding a contentsignal to generate scalable encoded data comprising data associated witha plurality of compression rates; determining compression factorindicators indicating data associated with the plurality of compressionrates; and generating combined data comprising the scalable encoded dataand the compression factor indicators.

These and other aspects, features and advantages of the invention willbe apparent from and elucidated with reference to the embodiment(s)described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will be described, by way of exampleonly, with reference to the drawings, in which

FIG. 1 illustrates an apparatus for content signal processing inaccordance with an embodiment of the invention; and

FIG. 2 illustrates an apparatus for processing a plurality ofapplications in accordance with an embodiment of the invention

DESCRIPTION OF PREFERRED EMBODIMENTS

The following description focuses on an embodiment of the inventionapplicable to processing of a video signal but it will be appreciatedthat the invention is not limited to this application but may be appliedto many other content signals including for example audio or multimediacontent signals.

FIG. 1 illustrates an apparatus 100 for content signal processing inaccordance with a preferred embodiment of the invention.

The apparatus 100 comprises a scalable encoder 101 which receives avideo signal from a suitable source (not shown) which may be an internalor external source. In the preferred embodiment, the received videosignal is a raw digitised video signal which has not been encoded orcompressed. In other embodiments, the video signal may already have beenencoded and/or compressed in a suitable format.

The scalable encoder 101 is operable to encode the received video signalsuch that it can fit into a given frame memory size. The scalableencoder 101 of the preferred embodiment uses the algorithm described in“DCT-domain embedded memory compression for hybrid video coders” by R.P. Kleihorst and R. J. van der Vleuten, Journal of VLSI SignalProcessing Systems, vol. 24, pp 1523-1543, 2000, Institute of Electricaland Electronic Engineers.

The scalable encoder 101 thus produces a signal which can be scaled tofit into a given memory allocation. Specifically, the scalable encoder101 divides a frame of the received video signal into a number of 8 by 8pixel blocks. A Discrete Fourier Transform (DCT) is performed on eachblock to generate spatial frequency coefficients. A number of frequencycoefficients are selected and encoded bitplane by bitplane (i.e. firstall most significant bits of all selected coefficients are included,then the next most significant bit of all selected coefficients and soon).

In the preferred embodiment, the video signal is stored in a framememory 103 coupled to the scalable encoder 101. In the preferredembodiment, the frame memory stores one or more frames in the DCTdomain, i.e. the selected coefficients of each DCT block are stored inbitplane order. Furthermore, in the preferred embodiment, the scalableencoder 101 is operable to scale the DCT encoded signal to fit the framememory 103 partly by selecting an appropriate number of coefficients andpartly by truncating the word size for different coefficients.

Thus, preferably, the scalable encoder 101 selects a number of lowfrequency coefficients and rejects a number of high frequencycoefficients for each DCT block The number of high frequencycoefficients that are rejected depends on the available memory capacityof the frame memory. Additionally or alternatively, the scalable encoder101 may truncate some of the least significant bits from some or all ofthe coefficients depending on the available memory capacity. This allowsfor a compressed video signal which suits the frame memory. In thepreferred embodiment, the scalable encoder 101 uses the full availablecapacity of the frame memory 103 regardless of the requirements of theintended application. Thus, even if an application is based on acompression factor of four, the scalable encoder 101 stores datacorresponding to a compression factor of two provided the frame memoryhas sufficient capacity.

In the preferred embodiment, the data stored in the frame memory 105thus corresponds to a plurality of compression rates. Specifically, theselection of the DCT coefficients and word sizes correspond to a firstcompression rate. However, if fewer DCT coefficients and/or reduced wordsizes are chosen, a higher compression rate could be achieved. Thus, thedata stored in the frame memory 105 comprises a subset of data whichcorresponds to a higher compression factor. Accordingly, depending onwhich data is extracted from the frame memory 105, signals withdifferent compression factors or rates can be obtained.

The scalable encoder 101 is further coupled to a compression processor105. The compression processor 105 is operable to determine compressionfactor indicators which indicate data associated with the plurality ofcompression rates.

In the preferred embodiment, the compression processor 105 determines anumber of compression factor indicators corresponding to a plurality offixed compression factors or equivalently to a number of equivalentframe sizes or data rates. For example, the compression processor 105may determine compression factor indicators for a compression factor of2, 4, 6 and 8. For each of these compression factors, compression factorindicators are determined that identify the data of the frame memory 105which should be extracted to generate a video signal having the desiredcompression factor.

It will be appreciated that the term compression factor may includeindirect references to compression factors such as a resulting datarate, frame memory size, compression rate or similar.

In the preferred embodiment, the compression factor indicators comprisepointers which point to the start point and termination point for dataof each compression factor. Thus, specifically, the scalable encodeddata of the scalable encoder 101 corresponds to a minimum compressionfactor achieved by including all data of the frame memory 105. For eachhigher compression factor, the compression processor 105 determineswhich data should be included to achieve this compression factor.Specifically, it determines which DCT coefficients should be includedand the word sizes of the selected coefficients. It then generatespointers for each block indicating the start and termination point ofthis data Depending on the organisation and data structure in the framememory 105, a plurality of start and termination pointers may begenerated for each DCT block. When all compression factor indicators aredetermined for one compression factor, the compression processor 105proceeds to determine pointers for the next higher compression factor.

As higher compression factors in the preferred embodiment are achievedby increasing truncation of high frequency coefficients and leastsignificant bits, the higher compression factors are achieved byidentifying a subset of the scalable encoded data selected by a lowercompression factor. Thus, the data comprises data sets which are nestedwithin each other such that higher compression factors are subsets ofthe lower compression factors. This may be used in reducing the numberof compression factor indicators needed since compression factorindicators indicating data of the higher compression factors may also beused for lower compression factors.

The compression processor 105 is coupled to the frame memory 105 and isoperable to store the compression factor indicators therein. Thus, theframe memory 105 comprises combined data comprising both the scalableencoded data from the scalable encoder 101 and the compression factorindicators from the compression processor 105.

It will be appreciated that in some embodiments, no frame memory 105 isused and the scalable encoded data and the compression factor indicatorsare combined for example by being included in a signal that may bedistributed to other functional units.

Accordingly, the apparatus 100 allows for combined data to be generatedthat can be scaled to suit a given limitation, such as a given memoryallocation, and which can be used to derive data signals havingdifferent compression rates. For example, an application may extractdata from a frame memory 105 in accordance with a compression factor offour whereas another application may extract data from the frame memoryin accordance with a compression factor of e.g. eight. No change isrequired in the scalable encoder 101 or the compression processor 105 orthe stored scalable encoded data for this to be achieved. Rather, theapplication may simply extract the required data. Indeed the twoapplications may extract data corresponding to different compressionfactors (and thus data rates etc.) substantially simultaneously. Hence,the embodiment allows for a very flexible and efficient system thatallows different applications with different requirements to use thesame single pass encoding and the same scalable encoded data generatedby that decoding.

FIG. 2 illustrates an apparatus 200 for processing a plurality ofapplications in accordance with a preferred embodiment of the invention.The apparatus incorporates the apparatus 100 of FIG. 1, and identicalfunctional modules are indicated by identical reference signs.

The apparatus 200 comprises a first extraction processor 201 which isoperable to determine a first compression factor associated with a firstapplication. In the preferred embodiment, the first compression factoris simply determined as a pre-stored value for the given application,but in other embodiments, the first extraction processor 201 is operableto determine the first application by analysing characteristics of theapplication or the content signal. For example, the first extractionprocessor 201 may comprise communication circuitry capable of exchangingthis information with the application.

The first extraction processor 201 is furthermore operable to extract afirst data set from the scalable encoded data which corresponds to thedetermined first compression factor. In the preferred embodiment, thefirst extraction processor 201 is coupled to a first cache memory 203where the first data set may be temporarily stored. Thus, in thepreferred embodiment, the first extraction processor 201 determines acompression factor for the stored frame in the frame memory 105 which issuitable for a first application. The first extraction processor 201then extracts the compression factor indicators corresponding to thefirst compression factor and subsequently extracts all data from theframe memory 105 which is indicated by the compression factor indicatorsto correspond to the first compression factor. Following this operation,the first cache memory 203 comprises a frame of the video signal havinga data size corresponding to the first compression factor.

The first cache memory 203 is coupled to a first decoder 205 which isoperable to convert the data of the frame stored in the first cachememory 203 into a suitable frame format for the subsequent processing bythe application. Specifically, the first decoder 205 may perform anInverse Discrete Cosine Transform (IDCT) to convert the DCT block databack into the spatial domain. However, the exact nature of the decodingwill depend on the requirements of the subsequent processing by thefirst application. Specifically, in some embodiments, the frame datafrom the frame memory 105 may be used directly without any interveningconversion.

The first decoder 205 is coupled to a second cache memory 207 and theconverted data is temporarily stored therein.

The second cache memory 207 is coupled to a first application processor209 which is operable to process the converted data set in accordancewith the first application. It will be appreciated, that the firstapplication may be any suitable application. However, in the preferredembodiment the first application is a segmentation application whichdivides the frame into a number of different image segments inaccordance with predefined criteria

Specifically, the segmentation application is preferably a timeconsistent pixel precise segmentation algorithm which is capable ofdividing the frame into image segments which have homogenous visualcharacteristics such as a similar colour or texture. Segmentation offrames is a complex process which may provide useful data for otherapplications including for example object recognition or videocompression applications.

In the preferred embodiment, the segmentation output is further used bythe first extraction processor 201 in extracting the first data set.Thus, in the preferred embodiment, the first application processor 209is coupled to the first extraction processor 201 such that thesegmentation data generated by the first application processor 209 isfed back to the first extraction processor 201. The first extractionprocessor 201 may then determine compression factors which vary across aframe depending on the segmentation data. This is particularly usefulfor time consistent segmentation wherein the segmentation of a givenframe may be applicable to a subsequent frame. For example, motionestimation of segments may be used to determine segmentation informationfor a subsequent frame. Hence, time consistent past information may beused in the extraction.

For example, a higher compression factor is determined for data blockswhich are wholly comprised within an image segment having homogenouscharacteristics such as substantially the same colour withoutsignificant texture. A lower compression factor may be determined forblocks in image segments which have high levels of texture or overlapedges between different image segments. Hence, the compression factorsmay be dynamically adjusted to correspond to the visual impact ofincreasing the compression and accordingly improved processing resultsmay be achieved.

In other embodiments, an external segmentation process may be used. Forexample, a given frame held in the frame memory may be analysedindependently and the derived segmentation information may be used toextract the first data set. This allows for an improved data extractionbased only on a spatial segmentation and does not necessitated timeconsistent segmentation or temporal correlation.

The apparatus of the preferred embodiment is furthermore capable ofprocessing a second application and is specifically capable ofprocessing the second application simultaneously with the firstapplication.

In the preferred embodiment, the apparatus further comprises a secondextraction processor 211 which is operable to determine a secondcompression factor which is associated with the second application. Thesecond compression factor is in the preferred embodiment different thanthe first compression factor.

It will be appreciated that the description for clarity and brevityrefers to a first and second compression factor but that this mayinclude a plurality of compression factors or ranges or intervals ofcompression factors. Furthermore, the first and second compressionfactor may comprise overlapping ranges of compression factors whichpreferably are not overlapping. For example, the first application maybe based on compression factors of 4, 6 and 8 and the first extractionprocessor 201 may extract data corresponding to one of these compressionfactors depending on e.g. the characteristics of an individual DCTblock. Similarly, the second application may be based on compressionfactors of 2, 4, 6 and 8, and data may be extracted corresponding to oneof these compression factors depending on e.g. the characteristics ofthe individual DCT block. Hence, the compression factors of the firstand second application may be similar or identical for some DCT blocksand different for other DCT blocks.

The second extraction processor 211 is furthermore operable to extract asecond data set from the frame memory 105 in response to the secondcompression factor.

In the preferred embodiment, the second extraction processor 211 iscoupled to the first extraction processor 201 and is operable to receivedata directly from this. In this embodiment, the second extractionprocessor 211 receives the common data of the first and second data setdirectly from the first extraction processor 201. Specifically, thecompression factor of the second application may correspond to a lowercompression factor than the first compression factor and the first dataset may be a subset of the second data set. Therefore, the secondextraction processor 211 receives the first data set directly from thefirst extraction processor 201. In addition, the second extractionprocessor 211 is coupled directly to the frame memory 105 and extractsadditional data therefrom. Thus, in this embodiment the secondextraction processor 211 directly extracts the data of the second dataset which has not been received from the first extraction processor 201from the frame memory 105.

Similarly, if the second data set is a subset of the first data set, thesecond extraction processor 211 may simply receive the subset of datafrom the first extraction processor 201 or may receive the entire firstdata set and discard the data which is not required.

Thus, the second extraction processor 211 may extract data from theframe memory 105 through the first extraction processor 201. Inparticular the first extraction processor 201 and the second extractionprocessor 211 may be the same functional module or unit.

Providing data to the second extraction processor 211 through the firstextraction processor 201 is particularly advantageous in situationswhere the apparatus 100 of FIG. 1 is implemented by external unitswhereas the remaining functional modules are implemented on a singleintegrated circuit. Thus, in embodiments employing a large frame memory,this may be implemented by off-chip external memory and the access ofthe external memory may be minimised. Hence, the implications of thebandwidth limitation and delay associated with accessing external memorymay be reduced.

The apparatus 200 further comprises a third cache memory 213, equivalentto the first cache memory 203, and allowing for a temporary storage ofthe second data set. The second cache memory 213 is coupled to a seconddecoder 215 which is operable to convert the data of the frame stored inthe third cache memory 213 into a suitable frame format for the secondapplication. The performance of the second decoder 215 is in thepreferred embodiment equivalent to that of the first decoder 205 andwill therefore not be described in further detail. The second decoder215 is coupled to a fourth cache memory 217 and the converted data istemporarily stored therein.

The fourth cache memory 217 is coupled to a second application processor219 which is operable to process the converted data set in accordancewith a second application. It will be appreciated that the secondapplication may be any suitable application. However, in the preferredembodiment, the second application is a video encoding/compressionapplication which is operable to encode the video signal into a digitalvideo signal in accordance with a defined standard such as MPEG2.

Methods and algorithms for encoding a video signal in accordance withe.g. the MPEG2 standard are well known in the art and will not bedescribed in further detail.

In some embodiments, the first and second application are capable ofinteracting and specifically segmentation data of the first applicationmay be fed to the second application and used in the video compressionalgorithm. This allows for a compression to be dynamically optimised forthe different identified image segments. Thus a high compression may beused for homogenous segments having little texture whereas lesscompression is used for segments having high texture levels and/or areasassociated with borders between segments. Furthermore, the segmentationdata may be used for object detection and for motion estimation.

In the preferred embodiment, the second application processor 219 isadditionally coupled to the fourth cache memory 217 and is operable tostore the compressed video data therein. Thus, the compressed dataframes may be stored and used for compression of subsequent framesthereby facilitating motion estimation, object tracking and other videocompression techniques.

In the preferred embodiment, most or all functional elements areimplemented in a single integrated circuit. Thus, in the preferredembodiment the frame memory and even the scalable encoder 101 and thecompression processor 105 are embedded on the same integrated circuit asthe remaining processing functionality. However, in other embodimentsother distributions are possible and specifically the interface betweenon-chip and off-chip functionality may be at the input to or the outputfrom the frame memory.

The invention can be implemented in any suitable form includinghardware, software, firmware or any combination of these. However,preferably, the invention is implemented at least partly as a dedicatedintegrated circuit or computer software running on one or more dataprocessors and/or digital signal processors. The elements and componentsof an embodiment of the invention may be physically, functionally andlogically implemented in any suitable way. Indeed the functionality maybe implemented in a single unit, in a plurality of units or as part ofother functional units. As such, the invention may be implemented in asingle unit or may be physically and functionally distributed betweendifferent units and processors.

Although the present invention has been described in connection with thepreferred embodiment, it is not intended to be limited to the specificform set forth herein. Rather, the scope of the present invention islimited only by the accompanying claims. In the claims, the termcomprising does not exclude the presence of other elements or steps.Furthermore, although individually listed, a plurality of means,elements or method steps may be implemented by e.g. a single unit orprocessor. Additionally, although individual features may be included indifferent claims, these may possibly be advantageously combined, and theinclusion in different claims does not imply that a combination offeatures is not feasible and/or advantageous. In addition, singularreferences do not exclude a plurality. Thus references to “a”, “an”,“first”, “second” etc do not preclude a plurality.

1. An apparatus (100) for content signal processing comprising: encodingmeans (101) for encoding a content signal to generate scalable encodeddata comprising data associated with a plurality of compression rates;means (103) for determining compression factor indicators indicatingdata associated with the plurality of compression rates; and means (105)for generating combined data comprising the scalable encoded data andthe compression factor indicators.
 2. An apparatus as claimed in claim 1further comprising: first processing means for processing a firstapplication, the first processing means comprising; means (201) fordetermining at least a first compression factor associated with thefirst application; first extraction means (201) for extracting a firstdata set associated with the first compression factor of the scalableencoded data in response to the compression factor indicators; means(203, 205, 207, 209) for processing the scalable encoded data inaccordance with the first application.
 3. An apparatus as claimed inclaim 2 wherein the first application is a segmentation application. 4.An apparatus as claimed in claim 3 wherein first extraction means (201)is operable to extract the first data set in response to a segmentationdetermined by the first application.
 5. An apparatus as claimed in claim2 further comprising second processing means for processing a secondapplication, the second processing means comprising: means (211) fordetermining a second compression factor associated with the secondapplication; the second compression factor being different than thefirst compression factor; second extraction means (211) for extracting asecond data set associated with the second compression factor of thescalable encoded data in response to the compression factor indicators;and means (203,205, 207, 209) for processing the scalable encoded datain accordance with the second application.
 6. An apparatus as claimed inclaim 5 wherein the first extraction means (201) is operable to senddata of the first data set associated with the second compression factorto the second processing means and the second extraction means (211) isoperable to extract additional data associated with the secondcompression factor.
 7. An apparatus as claimed in claim 5 wherein thefirst extraction means (201) is operable to send data of the first dataset associated with the second compression factor to the secondprocessing means and the second extraction means (211) is operable todiscard data not associated with the second compression factor.
 8. Anapparatus as claimed in claim 5 wherein the second application is acompression application.
 9. An apparatus as claimed in claim 5 whereinthe second processing means (211) comprises a data storage (213, 217)for storing the second data set; and wherein the second application isoperable to store compressed data in the data storage and comprises acompression algorithm operable to perform compression in response to thestored compressed data.
 10. An apparatus as claimed in claim 5 whereinthe first application is a segmentation application and the firstprocessing means is operable to provide segmentation data of thesegmentation application to the second processing means and thecompression application is operable to perform compression in responseto the segmentation data.
 11. An apparatus as claimed in claim 2 whereinthe first data set corresponds to a frame of the scalable encoded dataand the first extraction means (201) is operable to extract the firstdata set in response to a segmentation of the frame.
 12. An apparatus asclaimed in claim 1 wherein the encoding means (101) comprise a singlepass scalable encoder.
 13. An apparatus as claimed in claim 1 whereinthe compression factor indicators comprise at least one pointerindicating a termination point for data associated with a givencompression factor.
 14. An apparatus as claimed in claim 1 wherein thecompression factor indicators comprise at least one pointer indicating astart point for data associated with a given compression factor.
 15. Anapparatus for content signal processing comprising: receiving means(201) for receiving combined content signal data comprising scalableencoded data comprising data associated with a plurality of compressionrates and compression factor indicators indicating data associated withthe plurality of compression rates; means (201) for determining at leasta first compression factor associated with a first application;extraction means (201) for extracting a first data set associated withthe first compression factor of the scalable encoded data in response tothe compression factor indicators; and means (203,205, 207, 209) forprocessing the first data set in accordance with the first application.16. A method of content signal processing comprising the steps of:encoding a content signal to generate scalable encoded data comprisingdata associated with a plurality of compression rates; determiningcompression factor indicators indicating data associated with theplurality of compression rates; and generating combined data comprisingthe scalable encoded data and the compression factor indicators.
 17. Amethod as claimed in claim 16 further comprising the steps of:determining at least a first compression factor associated with thefirst application; extracting a first data set associated with the firstcompression factor of the scalable encoded data in response to thecompression factor indicators; processing the scalable encoded data inaccordance with the first application.
 18. A computer program enablingthe carrying out of a method according to claim
 17. 19. A record carriercomprising a computer program as claimed in claim 18.